Process for refining crude borax



i 5 um arsenate to form double salts, such,.-as',

Patented Dec." 10, 1929 UNITED STATES:

PATENT OFFICE 'crrAnLns Er.- monm Ann wInLIAu A; man, or TRONA, c LrsemvIA, Assrenons, BY ussnn ASSIGNIENIS, :ro' AMERICAN ,rorAsn a cannon. conronArxon, or NEW YORK; iv. in, A CORPORATION 01- nnLAwAnn A rnoc nss ro'a zsnrmme cnnnn BonAx Io Drawing.

This invention relates especially to refining crude borax such ,as that obtained from the evaporation and manipulation" of certain naturalvalkaline brines such as the brine of 5 Sear'les-Lake, California.

Inthe above analysis'we have exressed the total boric oxide (13 0,) content 0 :this brine in the terms of sodium tetraborate. However m in such brine there is always present a certain amount of sodium metaborate- (NQB 'OQ We have found that this sodium metaborate which is of itself quite soluble, reacts with the trisodium phosphate and the trisoditemperature at which the briiidi's found; I that is, about 22 C. We have also found thatthe brine of. Searles Lake will not dissolve borax at the temperature at which it occurs,

that is to say, the natural brine is saturated with borax at 22 C. o By combining thesephenomenaiof our discovery we are ablel tonefine borax a vary so eficie'ntand satisfactbry manner.

' proces of our invent on. r g v The process of our-inventlon possesses urge Application filed October 8, 1926. Serial No. 140,415.

In operatin a closed cycle'in which the end liquors o the process are continuously returned for further evaporation, the phosphate and arsenate accumulate in the liquors and are subsequently precipitated in the crude borax in proportion to their respective concentrations in the natural'brin We have found certain crudeborax, 0b

tained by the evaporation and manipulation of Searles Lake brine to have approximately the following composition:

the following description of our inven-- tion we shall-referto a borax containing ap preciable quantities ofphosphate. and arsenate impurities, suclr'as the above, as crude borax.

A It is in the refining of gush a crude-hams that our invention is of special value. One method which has been racticed in the refining of crude borax is' t at-of dissolving the same-in hot waterand recovering the we borax from the solution by a process of, ac

tional crystallization, This process is costly and ineflicient. In such a process it has been found necessary to heating the so ution-to dissolve the crude borax and subsequently for cooling the solusupply energy both for tion to- 'th'e. desired temperature to precipitate A the refined b'orax; Furthermore such aprocess is also ineflicient in thata certain quantity.

of the dissolving liquor must bevdiscarded in "orderto disposc of the phosphate and arse nate impurities; In discarding this liquor a certainramount ofborair in solutionis discarded, rendering :the process ineflieisnt and costly. A V j 7 Processes for removingjthe ghosphate and arsenate from the solutiomsue isfactory from an operating' of the above. mentiiined disadvii th PM of ur nas i s 15% I? eP iPita I .tion with calcium 'aalts, although highly sattue of the fact that no energy is expended in heating and cooling.

- y Another advantage in favor of the process of our invention is the brine used to remove the impurities from the crude borax is readily available and the cost of materials is therefore practically negligible.

The following is a description of one meth- 0d of carrying out the process of our invention. Five thousand pounds of crude borax having approximately the composition shown above are mixed with 2,500 gallons of natural brine at about 22 C. and the mixture agitatedby means of air for two hours. The leached crude borax is then removed by means of a centrifugal machine and given a slight washing with cold water to displace the brine adhering to the crystals. The resulting refined borax, which is dried to remove adherin moisture, weighs 4,100 pounds and has the ollowing composition:

Per cent Na ro. 0.13 Na AsO 0. 04 Na B O .10H O 99. 56

Moisture and undetermined. 27

TOmL; 100. 00

phosphate and arsenate impurities of the' crude borax may be discarded or subsequently treated to recover certain valuable constituents. Since the brine of Searles Lake may be had for the pumping, it is evident that the cost of material for the operation of our invention is extremely low.

Such a refinedborax is satisfactory as a commercial product; having a purity above 99% per cent. However, for certain special uses a more highly purified borax is' desirable. The refined bora'x, produced by the process of our invention, may be recrystallized from water to produce a nearly perfect borax. Since the purity of the refined borax produced by the'process of our invention is high, this second refining step may be carried out quite economically; for the same dis.-

' solving liquor may be used many times before the impurities have built up, to such a degree as to warrant its being discarded.

Although we have described our invention in the form in which we have found it most desirable and economical to employ it, we have found that certain advantages "may be gained by departing slightlyfrom the letter of the above description.

We have found that if the natural brine be of natural brine instead of 2,500 gallons as was the case when natural brine of 22 C. was used. Searles Lake brine at 32 C. will dissolve a certain small amount of borax, thereby slightly affecting the advantage to be gained by the use of a lesser quantity of naturalbrine.

Although we have stated that the phosphates and arsenates occur in the crude borax as the double salts shown above, we do not wish it impliedthat our invention relates specifically to the removal of these salts alone. We have found phosphate and especially arsenate impurities existing in the crude borax in forms other than those described above, and have successfully refined such crude borax by the methods previously described.

We have found it advantageous to modify the procedure of our invention slightly in certain cases especially as regards the removal of the lastmentioned arsenate impurities. We have found that a small quantity of an arsenical compound other than that previously described may be occluded within the borax crystal itself. In order to more completely remove such occlusions we have found It advantageous to heat the mixture of natural brine and borax to some temperature considerably above 22 C. By such a process the arsenate impurities are quite completely removed either by virtue of the complete solution of the borax crystals or'the increased reactivity'of the heated solvent, or both. The leached mass is then cooled to approximately 22 C. to recover the entire ori inal content of borax substantially freed rom all impurities. It is worthy of note that this modification of the process of our invention serves to. remove certain other undesirable occlusions, such. as organic matter.

We claim:

1. A process for refining crude borax consisting essentially in treating crude borax with natural brine substantially saturated with respect to borax, effecting the solution of the impurities of the borax in the brine, and separating the leached borax from the brine containing the dissolved impurities.

2. A process for refining crude borax consisting essentially in treatin crude borax with natural brine substantially saturated with borax, agitating the solution to dissolve the impurities of the borax in the brine, and

separating the leached borax from the brine 4. The process of refining crude borax consisting essentially in treating 5,000 pounds of crude borax with 2 gallons 9? See Lake brine at a temperature of 22 C., effect-- ing the solution of the impurities of the borax in the brine, and separating the-- which phosphate and arsenate compounds. are present as impurities, which comprises diiestin'g the crude borax in a body of Searles ake brine at a raised temperature until the phosphate and arsenate have dissolved,

and then filtering and drying the refined borax. i Y i 8. The process of refining crude borax which comprises treating crude borax with Searles Lake brine, filtering, and then recrystallizing from water.

tures. 7

CHARLES F. RITCHIE. WILLIAM A. GALE.

In testimony" whereof we affixfour signa- 

